Audio error converting matroska to DVD

[LoafingOaf]

Hi folks. If anyone's able to help with this, I'd be greatly appreciative.

I'm trying to convert from a hi-def(4.37Gig) mkv file, and keep getting this error;

Stream #0.0, 0.33 fps(r): Video: h264, yuv420p, 1280x544
Stream #0.1: Audio: 0x0000, 48000 Hz, 5:1
Output #0, dvd, to '/Users/adamford/Desktop/Torrents/Suspiria.1977.720p.BluRay.x264-CiNEFiLE.mkv.ff.mpg':
Stream #0.0, 25.00 fps(c): Video: mpeg2video, yuv420p, 1280x544, q=2-20, 83 kb/s
Stream #0.1: Audio: ac3, 48000 Hz, 5:1, 448 kb/s
Stream mapping:
Stream #0.0 -> #0.0
Stream #0.1 -> #0.1
Unsupported codec (id=86021) for input stream #0.1

Anything that can be done about this, or is there something in the original file causing ffmpegx to have a fit?
Thanks!

[Baldrick]

Buy the movie instead.